A relative occasionally makes PowerPoint presentations when she travels, but she is looking for a capability that I don't think it has.

When she displays a slide of a complex flowchart, she wants to be able to move around it at random, zooming in on various areas or pathways to make them visible. This would be in answer to questions from the audience, so she cannot predict in advance what needs to be enlarged.

Prezi lets you zoom in on areas, but I think you have to program the areas in advance. (I may be mistaken about this.)

If it's a windows machine, the easiest way if it's just to enlarge the stuff on the screen is to use the magnifier under the accessibility tools or Ease of Access depending on which version you have.

If there is not enough detail on what's on the screen, that won't work and you may have to build something with large and small images. If for example you divide the flowchart into eight images side by side in a table or something you can use animation to have larger versions of each of those sections hidden under it.

Check out this demo of a technique this guy used with two pictures and animation (to prevent the loss of quality from the standard zoom)